JP2001301640A - Lane maintaining device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To miniaturize a steering actuator generating the steering torque for maintaining a lane and to reduce its output power. SOLUTION: The target control liquid pressure Pai of a hydraulic cylinder 34 forming an active suspension is corrected according to a target front wheel steering angle calculated by automatic steering control. The roll rigidity distribution on the rear wheel side is increased to improve a turning property as the target front wheel steering angle becomes larger, and the roll rigidity distribution on the front wheel side is increased to improve the travel stability of a vehicle. Since the control quantity of the steering wheel by the steering actuator can be reduced by the changed quantity of the steering characteristic, the steering actuator can be miniaturized, and its output can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lane keeping apparatus which keeps a running vehicle in a lane.

[0002]

2. Description of the Related Art As a lane keeping apparatus for keeping a running vehicle in a lane, for example, Japanese Patent Application Laid-Open No. H11-9649.
There is one described in Japanese Patent No. This calculates the lateral shift amount of the traveling position of the vehicle from the reference position of the traveling lane,
A steering control torque that the driver can easily overcome is calculated based on the lateral deviation amount, and the steering control torque is generated in a direction to reduce the lateral deviation amount so as to maintain the vehicle in the traveling lane. Also, it is determined whether or not the own vehicle has crossed another driving lane adjacent thereto, and when it is determined that the own vehicle has crossed another driving lane, a sudden change in the control torque is suppressed, and a decrease in the riding comfort after the vehicle is over. The behavior of the vehicle is prevented from becoming unstable.

[0003]

As described above, when the steering control torque for reducing the lateral displacement is generated in accordance with the lateral displacement, as the lateral displacement increases, the steering control torque increases.
The steering control torque for reducing the lateral displacement amount also increases. This means that a sufficient steering actuator for generating the steering control torque is required. However, from the viewpoint of space efficiency and energy efficiency, it is desired to reduce the size of the steering actuator and make it a small output type. It is rare.

Accordingly, the present invention has been made in view of the above-mentioned conventional unsolved problem, and it is possible to reduce the size and output of a steering actuator for generating a steering torque for maintaining a lane. It is intended to provide a simple lane keeping device.

[0005]

To achieve the above object, a lane keeping apparatus according to a first aspect of the present invention calculates a target steering angle of a steered wheel for keeping a lane, and calculates the target steering angle and the target steering angle. An automatic steering unit that controls a steering actuator so that the actual steering angle of the steered wheels coincides with the actual steering angle to selectively control the steered wheels, and a steering characteristic changing unit that can change a steering characteristic of the vehicle, The steering characteristic changing unit improves the turning performance of the vehicle when the steered wheels are controlled by the automatic steering unit, when the steering amount of the steered wheels is large or when the steering amount is controlled to increase. When the steering amount is small or when the steering amount is controlled to decrease, the steering characteristic is changed in a direction to improve the running stability of the vehicle. It is characterized in that is adapted to change.

According to the first aspect of the present invention, a target steering angle of a steered wheel for maintaining a lane is calculated, and a steering actuator is controlled so that the target steering angle matches an actual steering angle of the steered wheel. The steered wheels are controlled. At this time, when the steering actuator is controlled by the automatic steering means and the steered wheels are controlled, the steering characteristic of the vehicle is changed by the steering characteristic changing means, and the steering amount of the steered wheels, that is, the actual steering angle of the steered wheels increases. When the vehicle is controlled in the direction of turning, or when the steering amount is large, the steering characteristic is changed in a direction to improve the turning performance of the vehicle. As a result, the turning performance of the vehicle is improved, so that the steering amount to be controlled by the steering actuator is correspondingly small. Further, when the steering amount of the steered wheels is controlled to decrease or the steering amount is small, the steering characteristics are changed in a direction to improve the running stability of the vehicle. This improves the running stability of the vehicle,
The steering amount to be controlled by the steering actuator can be reduced accordingly.

Therefore, the amount of steering to be controlled by the steering actuator can be reduced, which means that the steering actuator can be reduced in size and output. Further, in the lane keeping apparatus according to claim 2, the automatic steering means is configured to control the steering wheel according to a yaw angle of the vehicle with respect to the traveling lane, a lateral deviation of the vehicle in the traveling lane, and a curvature ahead of the traveling lane. Is controlled.

In the invention according to the second aspect, the automatic steering means controls the steered wheels according to the yaw angle of the vehicle with respect to the travel lane, the lateral deviation of the vehicle in the travel lane, and the curvature in front of the travel lane. As a result, the steered wheels can be accurately controlled according to the position of the host vehicle in the traveling lane and the situation ahead of the traveling lane. Further, in the lane keeping device according to claim 3, the steering characteristic changing means can change a roll rigidity distribution control device that can change a roll rigidity distribution before and after the vehicle, and can change a driving force distribution before and after the four-wheel drive vehicle. It is a driving force distribution control device, a four-wheel steering control device capable of steering control of front wheels and rear wheels, or a differential limit control device capable of changing a differential limit amount of drive wheels.

According to a fourth aspect of the present invention, in the lane keeping device, the roll rigidity distribution control device changes a steering characteristic by changing a damping force for damping vehicle body vibration at a front wheel position and a rear wheel position. When improving the turning performance, the damping force at the rear wheel position is made larger than the damping force at the front wheel position, and when improving the running stability of the vehicle, the damping force at the front wheel position is made larger than the damping force at the rear wheel position. It is characterized by becoming.

According to a fifth aspect of the present invention, in the lane keeping device, the driving force distribution control device changes a steering characteristic by changing a distribution ratio of a driving force transmitted from a driving source to front wheels and rear wheels. When the turning performance of the vehicle is improved, the distribution of the driving force to the rear wheels is increased. When the running stability of the vehicle is improved, the distribution of the driving force to the front wheels is increased.

According to a sixth aspect of the present invention, there is provided a lane keeping device, wherein the four-wheel steering control device changes a steering characteristic by changing a steering amount of a non-steered wheel to improve a turning characteristic of the vehicle. When the steering amount of the wheels to the same phase is reduced and the running stability of the vehicle is improved, the steering amount of the non-steered wheels to the same phase is increased.

According to a seventh aspect of the present invention, in the lane keeping device, the differential limiting control device changes a steering characteristic by changing a differential limiting amount of a driving wheel, and improves a turning characteristic of the vehicle during turning acceleration. When improving, the differential limiting amount is increased to improve the running stability of the vehicle, and the differential limiting amount is decreased. During turning braking, the differential limiting amount is increased when improving the turning performance of the vehicle. It is characterized in that the differential limiting amount is increased when the distance is reduced to improve the running stability of the vehicle.

[0013] In the invention according to claims 3 to 7, the steering characteristic changing means changes the damping force of the shock absorber or changes the hydraulic pressure of the hydraulic cylinder of the active suspension, for example. Roll stiffness distribution control device that can change the roll stiffness distribution before and after, a driving force distribution control device that changes the driving force distribution on the front wheel side and the rear wheel side of a four-wheel drive vehicle, and non-steered wheels that steer and control non-steered wheels Either the steering control device or the differential limiting control device that changes the differential limiting amount of the drive wheels, it is possible to easily change the steering characteristics by using these.

Further, a lane keeping device according to claim 8 is provided with turning degree detecting means for detecting a turning degree of the vehicle, and the steering characteristic changing means is constituted by a plurality of control devices among the control devices. It is characterized in that the control device to be operated is switched according to the turning degree detected by the turning degree detecting means. Claim 8
In the invention according to the invention, the steering characteristic changing means includes a roll rigidity distribution control device capable of changing the roll rigidity distribution before and after the vehicle, a driving force distribution control device capable of changing the front and rear driving force distribution of the four-wheel drive vehicle, the front wheels, and It consists of a plurality of non-driving wheel steering control devices that can control the rear wheels and a differential limiting control device that can change the differential limiting amount of the driving wheels. According to the degree, the control device to be operated to change the steering characteristics is switched.

Therefore, for example, in a region where the degree of turning is small, a non-steering wheel steering control device capable of obtaining a great effect by changing the steering characteristics in a region where the degree of turning is relatively small is operated, and conversely, turning is performed. In an area where the degree of turning is large, a large degree of turning can be obtained in a region where the degree of turning is relatively large, for example, by operating a roll stiffness distribution control device, a driving force distribution control device, or a differential limit control device. It is possible to obtain a sufficient effect by changing the steering characteristics regardless of whether the area is an area or a small area.

A lane keeping apparatus according to a ninth aspect of the present invention has a turning state detecting means for detecting a turning state of the vehicle, and the steering characteristic changing means determines that the turning state is detected by the turning state detecting means. It is characterized in that the steering characteristic is changed when it is detected. According to the ninth aspect of the present invention, the steering characteristic changing means changes the steering characteristic when the turning state detecting means detects the sharp turning state. It is possible to change the steering characteristics at the time when the effect of changing the characteristics can be sufficiently obtained.

Further, a lane keeping device according to a tenth aspect of the present invention has a vehicle behavior detecting means for detecting a vehicle behavior, and the steering characteristic changing means is configured to stabilize the running of the vehicle based on a result detected by the vehicle behavior detecting means. When the performance is predicted to be impaired, the steering characteristic is not changed in a direction to improve the turning performance of the vehicle.

According to the tenth aspect of the present invention, the steering characteristic is changed from the current vehicle behavior detected by the vehicle behavior detecting means in a direction for improving the turning performance of the vehicle.
When it is predicted that the running stability of the vehicle will be impaired,
The steering characteristics are not changed in a direction that improves the turning performance of the vehicle. Therefore, it is possible to prevent the running stability of the vehicle from being impaired due to the change in the steering characteristics.

[0019]

According to the lane keeping apparatus according to the first aspect of the present invention, when the steering actuator is controlled by the automatic steering means, control is performed when the steering amount of the steered wheels is large or the steering amount increases. When the steering characteristic is changed in the direction to improve the turning performance of the vehicle, the steering characteristic is changed in the direction to improve the running stability of the vehicle when the steering amount of the steered wheels is controlled to be small or the steering amount is reduced. Therefore, the steering amount to be controlled by the steering actuator can be reduced accordingly, and the steering actuator can be reduced in size and output.

Further, according to the lane keeping apparatus of the second aspect, the automatic steering means includes a yaw angle of the vehicle with respect to the traveling lane,
Since the steered wheels are controlled in accordance with the lateral deviation of the vehicle in the traveling lane and the curvature ahead of the traveling lane,
Steering wheels can be accurately controlled in accordance with the position of the host vehicle in the traveling lane and the situation ahead of the traveling lane. Further, according to the lane keeping apparatus according to claims 3 to 7, a roll stiffness distribution control device capable of changing the roll stiffness distribution before and after the vehicle, and a drive capable of changing the front and rear driving force distribution of the four-wheel drive vehicle. Since the steering characteristic is changed by any of the force distribution control device, the four-wheel steering control device capable of controlling the front wheels and the rear wheels, and the differential limit control device capable of changing the differential limit amount of the drive wheels, The steering characteristics can be easily changed.

Further, according to the lane keeping device of the eighth aspect, the control device that is operated to change the steering characteristic is switched according to the turning degree of the vehicle, so that even if the turning degree changes. Therefore, a sufficient effect by changing the steering characteristics can be obtained. Also,
According to the lane keeping device of the ninth aspect, the steering characteristic is changed when the turning state detecting means detects a sharp turning state, so that the steering characteristic can be changed at an appropriate timing.

Further, according to the lane keeping apparatus of the tenth aspect, when it is predicted that the running stability of the vehicle is impaired based on the detection result of the vehicle behavior detecting means, the turning direction of the vehicle is improved. Since the steering characteristic is not changed, it is possible to prevent the running stability of the vehicle from being impaired due to the change in the steering characteristic.

[0023]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a system configuration diagram showing a first embodiment of the present invention. In the figure, 1FL indicates a front left wheel, 1FR indicates a front right wheel, 1RL indicates a rear left wheel, 1RR indicates a rear right wheel, and a very common rack and pinion type steering mechanism is added to the front left and right wheels 1FL and 1FR. I have. This steering mechanism uses a rack 2 connected to the steering shaft (tie rod 2a) of the front left and right wheels 1FL, 1FR, a pinion 3 meshing with the rack 2, and a steering torque applied to the steering wheel 4 by the driver from the pinion 3. A steering shaft 5 to be rotated, and the rack 2, the pinion 3, the steering wheel 4, and the steering shaft 5 constitute a steering system.

A ring gear 6 constituting a speed reducer is coaxially fixed above the pinion 3 in the steering shaft 5, and a steering assist motor 7 is attached to the ring gear 6.
The ring gear 8 connected to the drive shaft is engaged, and the steering assist motor 7 is controlled to generate a steering assist force according to the steering torque by a duty-controlled pulse current output from a control unit 10 described below.
The power steering is constituted by the ring gears 6 and 8, the steering assist motor 7, and the control unit 10 for controlling the steering assist motor 7.

A steering torque sensor 12 constituting a torque detecting mechanism is provided above the ring gear 6 in the steering shaft 5. The torque detecting mechanism includes a torsion bar 12a connecting the lower end of the steering shaft 5 and the upper end of the pinion 3, and the steering torque sensor 12 disposed on the outer periphery thereof. The steering torque sensor 12 detects the steering torque from the amount of twist of the torsion bar 12a, and outputs a steering torque T which is a voltage signal corresponding to the magnitude of the steering torque.
Is supplied to the control unit 10.

Further, the front left and right wheels 1FL, 1FL are provided above the steering torque sensor 12 in the steering shaft 5.
An automatic steering mechanism for automatically steering the FR is also added. This automatic steering mechanism includes the steering shaft 5
And a drive gear 15 that meshes with the driven gear 14, and an automatic steering motor 16 that drives the drive gear 15 to rotate.
Note that a clutch mechanism 17 is interposed between the automatic steering motor 16 and the drive gear 15, and the clutch mechanism 17 is connected only during the automatic steering control. 16 is prevented from being input to the steering shaft 5. These mechanisms and the automatic steering motor 1
6 constitutes a steering actuator, which is controlled by a control signal from the control unit 10.

The power steering, the steering actuator, the steering torque sensor 12, and a steering angle sensor 21 described later constitute a steering mechanism 30. Various sensors are attached to this vehicle. Figure 21 is a steering angle sensor, the left and right front wheels 1FL from the rotation angle of the steering shaft 5, and outputs to the control unit 10 by indexing the actual front wheel steering angle [delta] _F of 1FR. Reference numerals 22FL to 22RR denote wheel speed sensors provided on each wheel, and output detection signals to the control unit 10.

Reference numeral 24 in the figure denotes an automatic steering switch for instructing execution of automatic steering control by the automatic steering mechanism. When the driver turns on the automatic steering switch 24, it detects "H". The signal is output to the control unit 10. In addition, a monocular camera 25 such as a CCD camera is installed in an inner mirror stay or the like in the vehicle interior, captures an image of a situation in front of the vehicle, and outputs captured image data to a camera controller 26. This camera controller 26
In the same manner as a known processing method, a lane marker near the own vehicle is detected by a process such as binarization, and a lateral deviation y in a traveling lane, a yaw angle Φ with respect to a tangent to the lane marker, A curvature β ahead of the traveling lane is calculated and output to the control unit 10.

Further, the vehicle body side member 32 and each wheel 1FL-
Hydraulic cylinders 34 are provided between 1RR, respectively, and constitute a known active suspension. The hydraulic pressure to each hydraulic cylinder 34 is controlled by a control unit 10 by a hydraulic control circuit (not shown), Roll control, bounce control, and pitch control are performed to stabilize the vehicle behavior.

A vertical acceleration sensor 36 for detecting a vertical acceleration acting in the vertical direction of the vehicle is provided at an appropriate position in the vehicle.
A longitudinal acceleration sensor 37 for detecting longitudinal acceleration acting in the longitudinal direction of the vehicle and a lateral acceleration sensor 38 for detecting lateral acceleration acting in the lateral direction of the vehicle are provided. The detection signals of these sensors are output to the control unit 10. . The control unit 10 is constituted by a discrete digital system such as a microcomputer (not shown). The control unit 10 drives the steering assist motor 7 based on detection signals from various sensors to generate steering on the steering shaft 5. A steering assist force corresponding to the torque T is generated. Also, the automatic steering switch 24
When the vehicle is operated in the ON state, known automatic steering control is performed, and drive control of the automatic steering motor 16 is performed so that the vehicle travels while maintaining the lane. Further, based on detection signals from various sensors, a posture change suppression control process in a known active suspension control device is executed, hydraulic pressure control for each hydraulic cylinder 34 is performed, and vehicle bounce control, roll control, and pitch control are performed. And stabilize the vehicle behavior. At this time, in the automatic steering control, when the number of steered wheels is increased by the automatic steering motor 16, the distribution of roll rigidity of the rear wheels is increased, and when the return is performed, the distribution of roll rigidity of the front wheels is increased. .

FIG. 2 is executed by the control unit 10.
Of automatic steering and attitude change suppression control processing
It is a flowchart which shows. This calculation processing is, for example,
10 msec. At the time of preset sampling such as
It is executed as a timer interrupt process every interval. Control
First, in step S1, the various kinds of sensors are set.
Read the detection signal from the That is, the steering angle sensor 2
1 is the actual front wheel steering angle δ _F, Wheel speed sensor
22FL to 22RR detection signal, automatic steering switch 24
Switch signal from the vertical sensor from the vertical acceleration sensor 36
Acceleration Z_Gi(I = FL to RR), longitudinal acceleration sensor 37
Longitudinal acceleration X from_GFrom the lateral acceleration sensor 38
Speed Y_GIs read, and the camera controller 26
The detected yaw angle Φ of the vehicle, the lateral deviation y from the center of the lane,
The curvature β of the traveling lane is read.

Next, the process proceeds to step S2, where the vehicle speed V is detected. For example, as shown in the following (1), the detection signals Vw _FL , Vw of the front wheel side wheel speed sensors 22FL, 22FR.
_The vehicle speed V is detected from the average value of _FR . V = (Vw _FL + Vw _FR ) / 2 (1) Next, the process proceeds to step S3, where the target front wheel steering angle δ ^* is set to the yaw angle Φ with respect to the traveling lane of the host vehicle and the lateral angle according to the following equation (2). It is calculated based on the deviation y and the curvature β of the traveling lane ahead.

Δ ^* = Ka · Φ + Kb · y + Kc · β (2) where Ka, Kb, and Kc are control gains that vary according to the vehicle speed. At this time, for example, rightward steering is represented by a positive value, and leftward steering is represented by a negative value. Next, the process proceeds to step S4, where the target control hydraulic pressure Pa _i (i is generated in the hydraulic cylinder 34 corresponding to each wheel.
= FL-RR), for example, vertical acceleration Z _Gi , lateral acceleration Y
_G, bounce motion control of the vehicle in the same manner as the known active suspension control on the basis of the longitudinal acceleration X _G, etc., rolling motion control amount is set based on the pitching motion control amount.

Here, the target control hydraulic pressure Pa is determined based on the vertical acceleration Z _Gi , the lateral acceleration Y _G , the longitudinal acceleration X _{G and the} like.
_Although the calculation of _i is performed, the present invention is not limited to this, and a vehicle height sensor or the like may be further provided to perform vehicle height control or preview control. You may. Next, the process proceeds to step S5, where it is determined whether or not the switch information from the automatic steering switch 24 is "on", that is, whether or not the automatic steering traveling is instructed. If the switch information is on, step S6 is performed.
Move to

In step S6, each target control hydraulic pressure P
Front wheel distribution ratio Dp of front and rear roll rigidity distribution based on a _i
Is calculated according to the following equation (3). Dp = Ps _F / (Ps _F + Ps _R ) (3) Ps _F = Pa _FL + Pa _FR Ps _R = Pa _RL + Pa _RR Next, the process proceeds to step S7, and the roll rigidity distribution ratio correction amount ΔDp is calculated by the following equation (4). ).

ΔDp = KS ₁ ││δ ^* │ (4) where KS ₁ is a control gain that changes according to the vehicle speed. For example, as shown in FIG. between to the threshold v ₁₁ of relatively medium speed is relatively large k
s _1H , the vehicle speed decreases as the vehicle speed increases from the threshold value v ₁₁ to the relatively high vehicle speed threshold value V ₁₂ , and becomes relatively small KS _1L when the vehicle speed exceeds the threshold value v _12. It is set as follows.

Next, the process proceeds to step S8, where the roll rigidity distribution front wheel distribution ratio Dp is corrected based on the roll rigidity distribution ratio correction amount ΔDp according to the following equation (5), and the roll rigidity distribution front wheel distribution ratio correction value Dph is calculated. I do. Dph = Dp−ΔDp (5) Next, the process proceeds to step S9, and the total values Ps _F and Ps of the target control hydraulic pressures Pa on the front wheel side and the rear wheel side according to the roll rigidity distribution front wheel distribution ratio correction value Dph. It corrected _R, to calculate a correction value Psh _F and Psh _R according to the following equation (6).

Psh _F = Dph · (Ps _F + Ps _R ) (6) Psh _R = (1−Dph) · (Ps _F + Ps _R ) Then, the process proceeds to step S10, where the front wheel side and the front wheel side calculated in step S9 are calculated. a correction value Psh _F and Psh _R of the total value of the target control hydraulic pressure of the rear wheel, the roll motor control amount of the left and right distribution ratio in accordance with the turning state calculated when calculating the target control pressure Pa _i in step S4 , The target control hydraulic pressure Pa _i of each wheel is corrected.

[0039] That is, according to the right and left distribution ratio corresponding to the turning state, prorated correction value Psh _F and Psh _R, which was added to the target control hydraulic pressure Pa _i of each wheel, the target control pressure The correction value Pah _i is calculated. Then, the process proceeds to step S11, and outputs a control signal for connecting the clutch mechanism 17, and then proceeds to step S12, to match the target front wheel steering angle [delta] ^* the actual front wheel steering angle [delta] _F from the steering angle sensor 21 , And outputs this to the automatic steering motor 16. Also generates a control signal for that can generate the target control hydraulic pressure correction value Pah _i in each of the hydraulic cylinders 34 and outputs this. Then, the process returns to the main program.

On the other hand, if the switch information from the automatic steering switch 24 is "OFF" in step S5, that is, if the automatic steering traveling is not instructed, the process proceeds to step S16, and a control signal for releasing the clutch mechanism 17 is issued. output, and then proceeds to step S17, generates a control signal for that can generate the target control pressure Pa _i in each of the hydraulic cylinders 34 and outputs this. Then, the process returns to the main program.

Here, the processing for controlling the steering actuator in the steering actuator and the control unit 10 corresponds to the automatic steering means, and the active suspension including the hydraulic cylinder 34 and the hydraulic cylinder 34 in the control unit 10 (not shown).
Corresponds to the steering characteristic changing means and the roll stiffness distribution control device.

Next, the operation of the first embodiment will be described. When the ignition switch is turned on, the control unit 10 starts automatic steering and attitude change suppression control processing, and also drives the steering assist motor 7 in accordance with the steering torque T from the steering torque sensor 12 to control the steering shaft. 5 generates a steering assisting force according to the steering torque generated in the steering wheel 5.

The camera controller 26 performs predetermined processing based on the detection signal of the monocular camera 25, and calculates the yaw angle Φ of the own vehicle, the lateral deviation y from the lane center, and the curvature β of the traveling lane. Then, this is output to the control unit 10. The control unit 10 inputs the various information from the camera controller 26 and reads information from various sensors (step S1).
The vehicle speed V is calculated based on the detection signals of the wheel speed sensors 22FL to 22RR (step S2), and the target front wheel steering angle δ ^* is calculated based on the above equation (2) (step S2).
3). Further, a pitching motion control amount, a roll motion control amount, and a bounce motion control amount are calculated based on the vertical acceleration Z _Gi , the lateral acceleration Y _G , the longitudinal acceleration X _{G, and the} like, and the target control hydraulic pressure Pa _i (i = FL) RR) (Step S4).

When the automatic steering switch 24 is in the off state, the flow proceeds from step S5 to step S1.
6 and outputs a control signal for separating the clutch mechanism 17 to output the steering shaft 5 of the automatic steering motor 16.
And outputs a control signal that sets the cylinder pressure of each hydraulic cylinder 34 to the target control hydraulic pressure Pa _i (step S17).

Thus, the cylinder of each hydraulic cylinder 34
Is the pitching motion control amount, roll motion control amount,
Target control hydraulic pressure Pa that can control uns movement control amount_iTona
Control, that is, normal posture change suppression control
Control is performed in the same manner as in the processing. And the automatic steering switch
When the switch 24 is controlled to be in the ON state, from step S5
Proceeding to step S6, the roll is determined based on the above equation (3).
A rigid distribution front wheel distribution ratio Dp is calculated. And this
Front wheel steering angle δ calculated in step S3 ^*Based on
Based on this, the correction amount ΔDp of the roll rigidity distribution front wheel distribution ratio is calculated.
(Step S7), and based on this, the roll rigidity is distributed.
The front wheel distribution ratio Dp is corrected (Step S8). Soshi
And the corrected roll rigidity distribution front wheel distribution ratio correction value Dp
h, the target control hydraulic pressure Pa_iIs corrected (step
Steps S9 and S10).

[0046] Here, the correction amount ΔDp, since ^* target front wheel steering angle [delta] is set to a larger value as large, the correction value Dph of the front wheel distribution ratio of roll stiffness distribution, the target front-wheel steering angle [delta] ^* is greater Set to a small value. Therefore, as shown in FIG. 4 (a), when the lateral deviation y increases in the automatic steering control process in a state where the vehicle is traveling straight, the target front wheel steering angle δ ^* increases accordingly, so that the roll rigidity is increased. The front wheel distribution ratio of the distribution becomes smaller and the roll rigidity distribution of the rear wheels increases, so the turning performance of the vehicle improves,
When the correction of the lateral deviation of the vehicle is completed in this state and the target front wheel steering angle δ ^* is reduced, the distribution of the roll stiffness of the rear wheels is reduced accordingly, and the stability of the vehicle is improved.

When the vehicle shifts from a straight running state to a turning state as shown in FIG. 4B, the target front wheel steering angle δ ^{* is} automatically set in the automatic steering control processing ^.
When the vehicle shifts from the straight running state to the turning state as shown in state A, the roll rigidity distribution ratio Dp is corrected in accordance with the target front wheel steering angle δ ^* , and the roll rigidity distribution of the rear wheels is reduced. It is corrected so as to increase, and the turning performance of the vehicle is improved.

Then, as shown in state B from this state, when correcting the lateral deviation y to the outside of the turn due to the vehicle being closer to the inside of the turn, the correction amount increases as the target front wheel steering angle δ ^* decreases. Since ΔDp decreases, the distribution of roll stiffness of the front wheels is corrected so as to increase, so that the straight running stability of the vehicle is improved, and the yaw damping of the vehicle can be improved. Modifications are made. When the correction is completed, the target front wheel steering angle δ ^*
As the roll stiffness distribution of the rear wheels increases with an increase in the number of wheels, the turning performance of the vehicle is improved.

At this time, the control gain KS ₁ used for calculating the correction amount ΔDp of the roll rigidity distribution ratio is set to a smaller value as the vehicle speed V increases, so that the correction amount ΔDp is suppressed to a smaller value as the vehicle speed increases. As a result, the front wheel distribution ratio is set to be relatively large, so that the vehicle high-speed stability is improved. As described above, when the target front wheel steering angle δ ^* increases, the turning performance of the vehicle improves, and conversely, the target front wheel steering angle δ
^{When *} decreases, the straight running stability of the vehicle improves,
In addition, since the corrected steering amount after the straight-ahead shift is small, the steering control torque for automatically controlling the steered wheels is small, that is, the load on the automatic steering mechanism including the automatic steering motor 16 is reduced. Therefore, downsizing and low output can be achieved. Further, the responsiveness of the automatic steering control can be improved.

In the first embodiment, the control unit 10 may also perform ABS control processing. In this case, the detection signals of the wheel speed sensors 22FL and 22FR are processed in step S2. Instead of calculating the vehicle speed V based on the vehicle speed V, the vehicle speed V calculated in the process of the ABS control process may be used. Also,
In the first embodiment, the target front wheel steering angle δ ^*
The case where the roll rigidity distribution ratio correction amount ΔDp is set according to the above has been described. However, the present invention is not limited to this, and the correction amount may be calculated according to the change amount Δδ ^* of the target front wheel steering angle δ ^*. Good. Further, a yaw rate sensor is further provided, and the target yaw rate φ is calculated based on the actual front wheel steering angle δ _F and the vehicle speed V.
_REF , and determines whether or not the yaw rate of the vehicle is in the convergence direction based on the target yaw rate φ _REF and the yaw rate φ detected by the yaw rate sensor, and calculates the roll rigidity distribution ratio correction amount ΔDp accordingly. You may make it.

In the above-described embodiment, the case where the active suspension is applied has been described. However, the present invention is not limited to this. For example, the actuator may be configured to be able to change the damping force of the damper steplessly or stepwise. By changing the magnitude of the damping force, the distribution of roll rigidity may be changed. Next, a second embodiment of the present invention will be described.

In the second embodiment, in a vehicle provided with a driving force distribution control device as steering characteristic changing means capable of controlling the distribution amount of front and rear driving force, the front and rear driving force distribution amounts are controlled. This changes the steering characteristics of the vehicle. FIG. 5 is a system configuration diagram showing the second embodiment.

The output from the engine 41 is shifted at the gear ratio selected by the transmission 42 and divided by the transfer 43 into the front wheel side and the rear wheel side. And the transfer 43
Are transmitted to the front wheels 1FL, 1FR via the front wheel output shaft 44, the front differential gear 45, and the front wheel drive shaft 46. On the other hand, the driving force of the rear wheel side is the propeller shaft 47, the rear differential gear 48, and the rear wheel side drive shaft 4.
9 to the rear wheels 1RL, 1RR.

The transfer 43 is provided with a known hydraulic multi-plate clutch mechanism 43a capable of changing the torque distribution ratio between the front and rear wheels according to the clutch control pressure applied from the hydraulic unit 50. The hydraulic unit 50
For example, a fluid pressure source 50a that pressurizes and supplies hydraulic oil in a reservoir (not shown) and a pressure control valve 50b that variably controls the hydraulic pressure supplied from the fluid pressure source 50a and supplies hydraulic oil to the clutch mechanism 43a. The pressure control valve 50b is configured to be controlled by the control unit 10.

Further, a wheel speed sensor 22 is provided at an appropriate position on the vehicle.
FL to 22RR, a lateral acceleration sensor 38, and a yaw rate sensor 42 for detecting an actual yaw rate φ generated in the vehicle are provided. As in the first embodiment, an automatic steering switch 24, a monocular camera 25, a camera controller 26, and a steering mechanism 30 are provided. And
The detection signals of the various sensors are output to the control unit 10, and the control unit 10 controls the steering mechanism 30 and the hydraulic unit 50.

The control unit 10 drives the steering assist motor 7 constituting the steering mechanism 30 based on the detection signals from the various sensors, and performs the steering torque generated on the steering shaft 5 in the same manner as in the first embodiment. The automatic steering control process is executed while generating a steering assisting force according to the above. Further, based on the detection signals from the various sensors, the front and rear drive torque distribution is determined in the same manner as the known front and rear drive force distribution control device, and the hydraulic unit 50 is controlled accordingly to control the clutch mechanism 43a. To control the front and rear drive torque distribution amounts. In the automatic steering control process, the drive power distribution amount of the rear wheels is increased when the number of steered wheels is increased, and the drive power distribution amount of the rear wheels is decreased when the return is performed.

FIG. 6 is a flowchart showing a processing procedure of the automatic steering and driving force distribution control processing executed by the control unit 10. This calculation processing is, for example, 1
0 msec. Is executed as a timer interrupt process at every preset sampling time. The control unit 10 first reads detection signals from various sensors in step S1, as in the first embodiment. That is, the actual front wheel steering angle δ _F from the steering angle sensor 21, the detection signals of the wheel speed sensors 22 FL to 22 RR, the switch signal from the automatic steering switch 24, the lateral acceleration Y _G from the lateral acceleration sensor 38, and the yaw rate sensor 42 The actual yaw rate φ is read, and the yaw angle φ of the vehicle detected by the camera controller 26, the lateral deviation y from the lane center, and the curvature β of the traveling lane are read.

Next, the process proceeds to step S2 to calculate the vehicle speed V from the above equation (1), and proceeds to step S3 to calculate the target front wheel steering angle δ ^* from the above equation (2). Next, the process proceeds to step S21, for example, in the same manner as the known front and rear driving force distribution control devices, for example, the respective wheel speed sensors 22FL to 22FL.
Front-rear wheel speed difference ΔV detected based on the detected value of 22RR
Then, based on the lateral acceleration Y _G and the like, the pressing pressure Te _REF of the clutch mechanism 43a of the transfer 43, that is, the driving torque of the front wheels is calculated.

Here, the pressing pressure Te _REF of the clutch mechanism 43a is calculated based on the front-rear wheel speed difference ΔV, the lateral acceleration Y _G and the like, but the present invention is not limited to this. Further, the accelerator opening, the longitudinal acceleration, and the like may be detected, and the calculation may be made in consideration of these, or any method may be used.

Next, the process proceeds to step S22, where the switch information from the automatic steering switch 24 is "ON", that is,
It is determined whether or not an automatic steering operation is instructed. If the switch information is on, the process proceeds to step S23. In this step S23, based on the following equation (7),
The vehicle side slip angle βc is calculated based on the actual yaw rate φ, the lateral acceleration Y _G , and the vehicle speed V.

Βc = Y _G −V · φ (7) Then, the process proceeds to step S24 to determine whether the calculated absolute value of the vehicle side slip angle βc is equal to or larger than the threshold value | β _TH | | ≧ | β _TH |) (vehicle behavior detecting means). If | βc | ≧ | β _TH |
25 and the pressing pressure Te of the clutch mechanism 43a.
The correction amount ΔTe _REF of _REF, is set to ΔTe _REF = 0.

On the other hand, in step S24, | βc | <| β _TH
If it is |, the process proceeds to step S26, and the correction amount ΔTe _REF of the pressing pressure is calculated based on the target front wheel steering angle δ ^* based on the following equation (8). ΔTe _REF = KS ₂ · | δ ^* | (8) where KS ₂ is a control gain that changes according to the vehicle speed. For example, as shown in FIG. A relatively large ks _2H until the vehicle speed reaches the threshold v _{21 in the} hit vehicle speed range, and the vehicle speed decreases as the vehicle speed increases from the threshold v ₂₁ to the threshold V _{22 in the} relatively high vehicle speed region. , the vehicle speed is set to be relatively small ks _2L becomes a threshold v ₂₂ or more.

Then, the process shifts to step S27 for pressing.
Correction amount of pressure ΔTe_REFBased on the clutch mechanism 43a
Pressure Te_REFIs corrected according to the following equation (9).
And the pushing pressure correction value Teh_REFIs calculated. Teh_REF= MAX (Te_REF−ΔTe_REF, 0) (9) Expression (9) is expressed by Te_REF−ΔTe_REFEither 0 or
The larger one is Teh_{RE F}Means to choose as
You.

Next, the process shifts to step S28 to
Output a control signal for connecting the switch mechanism 17, and then
Proceeding to step S29, the actual front wheel steering angle, that is, the steering angle
Actual front wheel steering angle δ from sensor 21_FIs the target front wheel steering angle δ^*When
A control signal for matching is generated, and this is
To the data 16. Also, the pressing pressure correction value Teh
_REFControl signal that can generate
Output to the unit 50. Then, the process returns to the main program.

On the other hand, if the switch information from the automatic steering switch 24 is "OFF" in step S22, that is, if the automatic steering traveling is not instructed, the flow shifts to step S31, where a control signal for separating the clutch mechanism 17 is issued. Output, and then the process proceeds to step S32, where the pressing pressure Te
_A control signal capable of generating _REF is generated and output to the hydraulic unit 50. Then, the process returns to the main program.

Next, the operation of the second embodiment will be described. Similarly to the first embodiment, when the ignition switch is turned on, the control unit 1
At 0, the automatic steering and driving force distribution control processing is started, and the camera controller 26 performs predetermined processing based on the detection signal of the monocular camera 25, and calculates the yaw angle Φ of the own vehicle, the lateral deviation from the lane center. y, the curvature β of the traveling lane is calculated. Then, this is output to the control unit 10.

The control unit 10 receives the various information from the camera controller 26, reads the information from various sensors, and controls the wheel speed sensors 22FL.
The vehicle speed V is calculated on the basis of the detection signals of the vehicle speeds 22 to 22RR, the target front wheel steering angle δ ^* is calculated (steps SS1 to S3), and the front and rear wheel speeds detected based on the detection values of the wheel speed sensors 22FL to 22RR are further calculated. The pressing pressure Te _REF of the clutch mechanism 43a is calculated based on the difference ΔV and the lateral acceleration Y _G (Step S21).

When the automatic steering switch 24 is in the off state, the process proceeds from step S22 to step S22.
Then, a control signal for releasing the clutch mechanism 17 is output to control the state in which the torque of the automatic steering motor 16 is not transmitted to the steering shaft 5, and step S32 is performed.
Then, a control signal for generating the pressing pressure Te _REF is generated and output to the hydraulic unit 50 (step S32).

As a result, the pressure control valve 50b of the hydraulic unit 50 is controlled, the clutch mechanism 43a is controlled, and the drive torque distribution amount is controlled according to the pressing pressure Te _REF. Control is performed similarly. Then, when the automatic steering switch 24 is controlled to be turned on, the process proceeds from step S22 to step S23, and calculates the vehicle sideslip angle βc based on the above equation (7).

Then, the side slip angle βc of the vehicle is | βc | <
When | β _TH |, the flow shifts from step S24 to step S26, and the correction amount ΔTe _{REF of the} pressing pressure is set based on the above equation (8), that is, the correction value is set to a larger value as the target front wheel steering angle δ ^* increases. Accordingly, the pressing pressure correction value Teh _REF is set to be smaller (step S27), and the correction is performed so that the pressing pressure on the front wheel side becomes smaller (step S28).

Therefore, as shown in FIG. 4A, when the lateral deviation y increases while the vehicle is traveling straight, the target front wheel steering angle δ ^* calculated in the automatic steering control increases. Accordingly, the pressing pressure on the front wheel side decreases, and the distribution of the driving force on the rear wheel side increases, and the turning performance of the vehicle improves. When the correction of the lateral deviation of the vehicle is completed from this state and the target front wheel steering angle δ ^* calculated in the automatic steering control becomes small, the driving force distribution amount on the front wheel side increases accordingly, and the stability of the vehicle is reduced. improves.

When the vehicle shifts from a straight running state to a turning state as shown in FIG. 4 (b), the target front wheel steering angle δ ^* increases accordingly. The pressing pressure of the clutch mechanism 43a is corrected in a direction to reduce the pressing pressure, and the amount of driving force distribution on the rear wheel side is increased, so that the turning performance of the vehicle is improved. Then, when the vehicle is turned toward the inside of the turn as shown in state B from the turning state, the target front wheel steering angle δ ^* is reduced because the automatic steering control attempts to correct the lateral deviation to the outside of the turn, and the correction amount accordingly increases. Since ΔTe _REF decreases, the driving force distribution amount of the front wheels is corrected so as to increase, the straight running stability of the vehicle is improved, and the correction to the outside of the turning of the vehicle is performed with smooth vehicle behavior.

At this time, since the control gain KS ₂ used for calculating the correction amount ΔTe _REF is set to a smaller value as the vehicle speed V increases, the correction amount ΔTe _REF is suppressed to a smaller value as the vehicle speed increases. Is set to be relatively large, so that the high-speed stability of the vehicle is improved. Also, the side slip angle βc of the vehicle is | βc | ≧ | β _TH |
, The process proceeds from step S24 to step S25, and the correction amount ΔTe _REF of the pressing pressure becomes zero.
The pressing pressure Te _REF is not corrected. Therefore, when the vehicle behavior is detected from the side slip angle βc of the vehicle, and it is determined that the stability of the vehicle is impaired, the steering characteristics based on the target front wheel steering angle δ ^* are not changed, and the turning characteristic of the vehicle is improved. The steering characteristics are not corrected, and the steering characteristics are controlled by controlling both the steering characteristics according to the current driving state by the driving force distribution control and the steering characteristics based on the target front wheel steering angle δ ^* by the automatic steering control. Can be prevented from being excessively improved, or the stability of the vehicle is deteriorated depending on the road surface condition.

Therefore, also in the second embodiment, the same operation and effect as in the first embodiment can be obtained. Note that, in the second embodiment,
Based on the target front wheel steering angle δ ^* , the correction amount Δ of the pressing pressure
The case where the Te _REF is calculated has been described. However, the present invention is not limited to this. For example, the target yaw rate φ ^* is calculated from the actual front wheel steering angle δ _F and the vehicle speed V, and the target yaw rate φ is calculated.
^* And the actual yaw rate φ to determine whether or not the yaw rate of the vehicle is in the convergence direction, and accordingly, the correction amount ΔTe _REF
May be calculated.

Further, in the above-described embodiment, the case where the front and rear driving force distribution ratios are continuously controlled as the driving force distribution control device has been described. For example, the four-wheel drive and the two-wheel drive are simply switched. The distribution of the front and rear driving force may be changed using an actuator. Next, a third embodiment of the present invention will be described.

In the third embodiment, in a vehicle equipped with a four-wheel steering control device as steering characteristic changing means for steering the front wheels and the rear wheels, the rear wheels serving as auxiliary steering wheels are subjected to steering control. By doing so, the steering characteristics of the vehicle are changed. FIG. 8 is a system configuration diagram showing the third embodiment.

In the figure, 1FL and 1FR are front wheels as main steering wheels, 1RL and 1RR are rear wheels as auxiliary steering wheels, and a tie rod 4 is provided between the front wheels 1FL and 1FR.
The same steering mechanism 30 as in the first embodiment is interposed. On the other hand, a steering shaft 52 is inserted between the rear wheels 1RL, 1RR via a tie rod 51, and the actuator unit 53 moves the steering shaft 52 in the left-right direction of the vehicle to assist the rear wheels. ing. The actuator unit 53 constitutes a known rear-wheel steering mechanism 55 using an electric motor 54 as a power source.
4 in both directions, the steering shaft 52 is reciprocated in the left-right direction of the vehicle, and the rear wheels 1R, which are auxiliary steering wheels, are driven.
L, 1RR can be steered synchronously in the left-right direction. The rear wheel steering mechanism 55, the rotation angle or the rear wheels 1RL of the electric motor 54, and wheel steering angle sensor 56a after detecting the actual rear wheel steering angle theta _R of 1RR 56
b is provided, and the detection signals of these sensors are input to the control unit 10.

Further, similarly to the first embodiment, wheel speed sensors 22FL to 22RR, an automatic steering switch 24, a monocular camera 25, and a camera controller 26 are provided at appropriate places in the vehicle. The detection signals of the various sensors are output to the control unit 10, which controls the steering mechanism 30 and the actuator unit 53.

The control unit 10 drives the steering assist motor 7 constituting the steering mechanism 30 on the basis of the detection signals from the various sensors and operates the steering torque generated on the steering shaft 5 in the same manner as in the first embodiment. The automatic steering control process is executed while generating a steering assisting force according to the above. Further, based on detection signals from various sensors, in the same manner as a known four-wheel steering control device, by performing rear-wheel steering in the same phase as steering of the front wheels by the steering wheel 4, in the middle vehicle speed range, Change the characteristics in the weak understeer direction to improve turning performance,
In the high-speed range, the steering characteristics are changed and controlled to be strengthened in the understeer direction, so that the stability of the vehicle at the time of turning, lane change, etc. is improved and the convergence of cornering is improved. Also, in the automatic steering control process, when the turning of the steered wheels is increased, the in-phase steering amount of the rear wheels is decreased and the reverse-phase steering amount is increased. And the amount of reverse-phase steering is reduced.

FIG. 9 is a flowchart showing the processing procedure of the automatic steering and rear wheel steering control processing executed by the control unit 10. This calculation processing is, for example, 10
msec. Is executed as a timer interrupt process at every preset sampling time. The control unit 10 first reads detection signals from various sensors in step S1. That is, the actual front wheel steering angle δ _F from the steering angle sensor 21 and the wheel speed sensors 22FL to 22RR
, The switch signal from the automatic steering switch 24, the actual rear wheel steering angle θ _R from the rear wheel steering angle sensors 56a and 56b, the yaw angle Φ of the host vehicle detected by the control unit 10, the lane center , And the curvature β of the traveling lane is read. And the rear wheel steering angle sensor 5
The abnormality of the rear wheel steering angle sensor is monitored by comparing the two actual rear wheel steering angles θ _R from 6a and 56b.

Next, the flow shifts to step S2, where the first
The vehicle speed V is detected in the same manner as in the embodiment of FIG.
Calculating the target front wheel steering angle [delta] ^* 3, for example analogously to known four-wheel steering control system in step S41, the actual front wheel steering angle [delta] _F from the steering angle sensor 21, also the actual front wheel steering angle [delta] _F The target rear wheel steering angle θr _REF is calculated based on the calculated steering angular velocity δ _F ′, vehicle speed V, and the like.

Here, the target rear wheel steering angle θr _REF is calculated based on the actual front wheel steering angle δ _F , the steering angular velocity δ _F ′, the vehicle speed V, etc. from the steering angle sensor 21. However, the present invention is not limited to this, and the lateral acceleration may be further detected and calculated in consideration of this, or may be calculated by any method. Next, the process proceeds to step S42, where it is determined whether or not the switch information from the automatic steering switch 24 is "ON", that is, whether or not the automatic steering is instructed. If the switch information is ON, the process proceeds to step S4.
Move to 3.

[0083] In the step S43, on the basis of the following equation (10) calculates a correction amount Derutashitaaru _REF of the target rear wheel steering angle [theta] r _REF. Δθr _REF = KS ₃ · θr _REF (10) In the expression, KS ₃ is a control gain that changes in accordance with the vehicle speed. For example, as shown in FIG. threshold v until ₃₁ is relatively large ks _3H vehicle speed, between the vehicle speed threshold value v ₃₁ to the threshold V ₃₂ of relatively high vehicle speed decreases as the vehicle speed increases, and the vehicle speed When the threshold value v ₃₂ or more is set, the value is set to be relatively small ks _3L .

Then, the process shifts to step S44 to correct the target rear wheel steering angle θr _REF based on the correction amount Δθr _REF according to the following equation (11), and to set the target rear wheel steering angle correction value θrh
Calculate _REF . θrh _REF = θr _REF −Δθr _REF (11) Then, the process proceeds to step S45, where a control signal for connecting the clutch mechanism 17 is output, and then, step S46 is performed.
Proceeds to the actual front wheel steering angle that is, generates a control signal for causing the actual front wheel steering angle [delta] _F from the steering angle sensor 21 is equal to the target front-wheel steering angle [delta] ^*, and outputs it to the automatic steering motor 16 . Further, it generates a control signal for obtaining the target rear wheel steering angle correction value θrh _REF and outputs it to the actuator unit 53. Then, the process returns to the main program.

On the other hand, if the switch information from the automatic steering switch 24 is "OFF" in step S42, that is, if the automatic steering traveling is not instructed, the flow shifts to step S48, where a control signal for releasing the clutch mechanism 17 is issued. And then proceeds to step S49, where the target rear wheel steering angle θ
A control signal for matching r _REF with, for example, the actual rear wheel steering angle θ _R from the rear wheel steering angle sensor 56a is generated and output to the actuator unit 53. Then, the process returns to the main program.

Therefore, when the automatic steering is not instructed, the process proceeds from step S1, S2, S3, S41 to step S49 from step S42 through step S48, where the target rear wheel steering angle θr _REF and the rear wheel steering angle sensor are detected. A control signal for matching the actual rear wheel steering angle θr from 56a is generated and output to the actuator unit 53, whereby the electric motor 54 of the actuator unit 53 is driven, and the rear wheels 1RL, 1RR are steered. The rear wheels are steered according to the target front wheel steering angle δ ^* , and normal rear wheel steering control processing is performed.

Then, the automatic steering switch 24 is turned on.
Control from step S42 to step S43
Then, based on the above equation (10), the target rear wheel steering angle θr
_REFCorrection amount Δθr_REFIs calculated. Where the correction amount
Δθr_REFIs the target front wheel steering angle δ^*The larger the
Correction value θrh for the target rear wheel steering angle.
_REFIs the target front wheel steering angle δ^*Value becomes smaller as
Is set to (step S44). In other words, in the in-phase direction
Steering amount decreases or the steering amount in the opposite phase increases.
As a result, the turning performance of the vehicle is improved. Conversely, the target front wheel steering angle δ
^*Becomes smaller, the amount of steering in the same phase of the rear wheel steering angle increases.
And the amount of steering in the opposite phase is reduced, and the stability of the vehicle is reduced.
Is improved.

Therefore, as shown in FIG. 4 (a), when the vehicle is traveling straight, the lateral deviation y occurs, and when the target front wheel steering angle δ ^* is increased in order to correct the lateral deviation y, it is correspondingly increased. Since the steering amount in the in-phase direction of the target rear wheel steering angle θr _REF is reduced or the steering amount in the opposite phase is increased depending on the steering speed, the turning performance of the vehicle is improved, and the lateral deviation from this state is improved. When the target front wheel steering angle δ ^* becomes smaller after the correction of the above, the steering amount in the in-phase direction of the target rear wheel steering angle θr _REF increases or the steering amount in the opposite phase direction decreases in response to this, Stability is improved.

When the vehicle shifts from a straight running state to a turning state as shown in FIG. 4B, the target front wheel steering angle δ ^{* is} automatically set in the automatic steering control processing ^.
Is increased, and if the target rear wheel steering angle θr _REF is in the in-phase direction, the correction is made in the direction of decreasing the same, and if the target rear wheel steering angle θr _REF is in the opposite phase, the correction is made in the direction of increasing, so that the turning performance of the vehicle is improved. Then, if the target front wheel steering angle δ ^* decreases to correct the lateral deviation of the vehicle that is closer to the inside of the turn, if the target rear wheel steering angle θr _REF is in the same phase direction, it is corrected in a direction to increase it, If it is in the opposite phase, the correction is made in the direction of decreasing, so that the straight running stability of the vehicle is improved.

At this time, since the control gain KS ₃ is set to a smaller value as the vehicle speed V increases, the correction amount Δθr _REF is suppressed to a smaller value as the vehicle speed increases, and the target rear wheel steering angle θr _REF is in the same phase direction. Sometimes it is corrected to a larger value, and when it is in the opposite phase direction, it is corrected to a smaller value, so that the high-speed stability of the vehicle is enhanced. Therefore, also in this case, the same operation and effect as those of the first embodiment can be obtained.

In the third embodiment,
The case has been described in which the correction amount Δθr _REF of the target rear wheel steering angle θr _REF is calculated based on the target front wheel steering angle δ ^* . However, the present invention is not limited to this, and a yaw rate sensor is further provided and the actual front wheel steering angle δ _F Target yaw rate φ from vehicle speed V
_REF is calculated, and it is determined whether or not the yaw rate of the vehicle is in the convergence direction based on the target yaw rate φ _REF and the yaw rate φ, and the correction amount Δθr _REF of the target rear wheel steering angle is calculated accordingly. It may be.

Further, as a steering characteristic changing means,
The four-wheel steering control device according to the third embodiment is combined with the active suspension according to the first embodiment, or the four-wheel steering control device according to the third embodiment and the two-wheel steering control device according to the second embodiment are combined. Combining with the driving force distribution control device according to the embodiment, detecting the lateral acceleration Y _G as turning degree detecting means, and changing the operating range of the means for changing the steering characteristics according to the magnitude of the lateral acceleration Y _G Thus, the control device may be operated in a region where the effect of each control device is large.

That is, the rear wheel steering control has a large effect in a region where the lateral acceleration is small, and the roll rigidity distribution control and the front and rear driving force distribution control processes have a large effect in a region where the lateral acceleration is large. When calculating the correction amount,
As shown in the following equation (12) to (14), for example, multiplying the coefficient Ky ₁ or Ky ₂ changes according to the lateral acceleration Y _G as shown in FIG. 11, be controlled on the basis of these Good.

ΔDp = Ky₁・ KS₁・ ｜ δ^*| (12) ΔTe_REF= Ky₁・ KS_Two・ ｜ δ^*| (13) Δθr_REF= Ky_Two・ KS_Three・ Δ^* (14) The coefficient Ky₁Is the lateral acceleration as shown by the broken line in FIG.
| Y_G| [G] becomes | y_G1| <1 [g]
Value | y_G1Is set to “0” while smaller than | y
_G1| <| Y_G2│ <1 [g] Threshold | y_G2|
If greater, it is set to "1" and | y_G1| <| Y
_G| <| Y_G2| While | Y_GAs | increases
Is set to increase from “0” to “1”. Ma
The coefficient Ky_TwoIs the horizontal curve as shown by the solid line in FIG.
Speed | Y_G| [G] is the threshold value | y_G1| Less than
The interval is set to “1” and the threshold value | y_G2|
When it is larger, it is set to “0”, and | y_G1| <| Y_G|
<| Y_G2| While | Y _GAs | increases
It is set to decrease from “1” to “0”.

By setting as described above, the lateral acceleration
Is relatively small, the coefficient Ky ₁Is "0", Ky_Two
Is set to “1”, the correction amount ΔDp or ΔTe
_REFBecomes zero, and roll stiffness distribution control or front and rear driving force
No correction of steering characteristics by distribution control
Is the correction amount Δθr_REFIs enabled and rear wheel steering control processing
The steering characteristics are corrected at
In the region where the degree is relatively large, the coefficient Ky₁Is “1”, Ky
_TwoIs set to “0”, the correction amount Δθr_REFIs zero
And the correction amount ΔDp or ΔTe_REFIs valid
From the roll stiffness distribution control or the front / rear driving force distribution control.
The steering characteristic is corrected.

Next, a fourth embodiment of the present invention will be described. The fourth embodiment is directed to a vehicle provided with a differential limit control device as steering characteristic changing means for performing optimal differential limit control of driving wheels in accordance with a driver's accelerator operation or brake operation. The steering characteristic of the vehicle is changed by controlling the operation control amount of the drive wheels.

FIG. 12 is a system configuration diagram showing the fourth embodiment. The output from the engine 41 is a transmission 42
The transmission is shifted by the gear ratio selected in
At the front wheels 1FL, 1FR and the rear wheels 1RL, 1RR. Then, the front wheel side driving force divided by the transfer 43 is transmitted to the front wheels 1FL, 1FR via the front wheel side output shaft 44, the front differential gear 45, and the front wheel side drive shaft 46. On the other hand, the rear wheel side driving force is transmitted through the propeller shaft 47, the differential limiting device 61, and the rear wheel side drive shaft 49 to the rear wheel 1 as a driving wheel.
RL, 1RR.

The transfer 43 has a built-in multi-plate clutch (not shown). The hydraulic pressure of the clutch is generated by a hydraulic unit (not shown) so that the driving force is transmitted to the front wheels in accordance with the clutch engaging force. Has become. The differential limiting device 61 includes a known differential limiting clutch 63 that can change the torque distribution ratio to the front and rear wheels according to the clutch control pressure applied from the hydraulic unit 62. The hydraulic unit 62 includes:
For example, a fluid pressure source 62a that pressurizes and supplies hydraulic oil in a reservoir (not shown) and a pressure control valve 62b that variably controls the hydraulic pressure supplied from the fluid pressure source 62a and supplies hydraulic oil to the differential limiting clutch 63 The pressure control valve 62b is configured to be controlled by the control unit 10.

As in the case of the first embodiment, a steering mechanism 30 is provided, and at the appropriate position of the vehicle,
Wheel speed sensors 22FL to 22RR, automatic steering switch 2
4, a monocular camera 25, a camera controller 26, a longitudinal acceleration sensor 37, a lateral acceleration sensor 38, an accelerator opening sensor 39, and a brake switch 40 are provided. The detection signals of various sensors are transmitted to the control unit 1.
0, the steering unit 30 is controlled by the control unit 10 and the hydraulic unit 6
2 is controlled.

The control unit 10 has the first
Similarly to the embodiment, based on detection signals from various sensors, the steering assist motor 7 included in the steering mechanism 30 is driven to generate a steering assist force corresponding to the steering torque generated in the steering shaft 5, and to automatically generate the steering assist force. Perform steering control. Also, based on detection signals from various sensors, in the same manner as a known differential limit control device, during turning acceleration, differential limiting is performed so as to cancel an understeer moment generated by a load movement, and a driving line as expected by the driver is provided. The differential is limited so as to cancel the oversteer moment during turning braking, so that stability is maintained during braking while turning. At this time, in the automatic steering control, when the steering amount of the steered wheels, that is, the steering angle is increased, the differential limit amount is increased during the turning acceleration, and the differential limit amount is decreased during the turning braking. Conversely, when the steering amount of the steered wheels is reduced in the control of the automatic steering motor, the differential limiting amount is reduced during turning acceleration and the differential limiting amount is increased during turning braking.

FIG. 13 is a flowchart showing the procedure of the automatic steering and differential limiting control processing executed by the control unit 10. This calculation processing is, for example, 1
0 msec. Is executed as a timer interrupt process at every preset sampling time. The control unit 10 first reads detection signals from various sensors in step S1. That is, the steering angle sensor 21
Front wheel steering angle δ _{F from} the wheel speed sensors 22FL to 22R
R, a switch signal from the automatic steering switch 24, a longitudinal acceleration X _G from the longitudinal acceleration sensor 37, a lateral acceleration Y _G from the lateral acceleration sensor 38, and a detection signal from the brake switch 40. , The yaw angle Φ of the own vehicle, the lateral deviation y from the center of the lane, and the curvature β of the traveling lane are read.

Next, the flow shifts to step S2, where the first
The vehicle speed V is detected based on the equation (1) in the same manner as in the first embodiment, and the target front wheel steering angle δ ^* is calculated in step S3. Then, the process proceeds to step S51, for example analogously to known differential limiting control apparatus, the left and right wheel speed difference based on the lateral acceleration Y _G right and left wheel speed detection value also turning state, whether it is during acceleration, The pressing pressure Td _REF of the differential limiting clutch 63 is calculated based on whether braking is being performed or the like.

Here, the pressing pressure Td _REF of the differential limiting clutch 63 is determined based on the lateral acceleration Y _G , the difference between the left and right wheel speeds, the turning state, whether the vehicle is accelerating or braking, and the like.
Is calculated, but the present invention is not limited to this. The slip state of the drive wheels may be detected and calculated in consideration of the slip state, or may be calculated by any method.

Next, the flow shifts to step S52, where the switch information from the automatic steering switch 24 is "ON", that is,
It is determined whether or not the automatic steering operation has been instructed. If the switch information is on, the process proceeds to step S53. In this step S53, the vehicle speed V and the lateral acceleration Y _G are | V | ≧ | V _TH | and | Y _G | ≧ | Y _GTH |
(Turning state detecting means). The threshold values V _TH and Y _GTH are set to values that can be regarded as making a sharp turn.

Then, | V | ≧ | V _TH | and | Y _G | ≧
When both | Y _GTH | are satisfied, the process proceeds to step S54, and the correction amount ΔTd _REF of the pressing pressure Td _REF is calculated based on the following equation (15). Then, step S56
Move to ΔTd _REF = KS ₄ · δ ^* (15) where KS ₄ is a control gain that changes according to the vehicle speed. For example, as shown in FIG. threshold v until ₄₁ is relatively large ks _4H vehicle speed, between the vehicle speed threshold value v ₄₁ to the threshold V ₄₂ of relatively high vehicle speed decreases as the vehicle speed increases, and the vehicle speed the threshold v ₄₂ or more when it is set to be relatively small ks _4L.

On the other hand, in step S53, the vehicle speed V and the lateral acceleration Y _G are | V | ≧ | V _TH | and | Y _G | ≧ | Y
_If not _GTH |, the flow proceeds to step S55, and the correction amount ΔTd _REF of the pressing pressure Td _REF is set to ΔTd _REF = 0. Then, control goes to a step S56. In this step S56, when it is determined that the pressing pressure Td _REF of the multiple disc clutch 63 is corrected based on the correction amount ΔTd _REF and acceleration is performed based on the detection signals of the accelerator opening sensor 39 and the brake switch 40. , The following equation (1
6), and when it is determined that braking is being performed, the correction is made based on the following equation (17).

Tdh_REF= Td_REF+ ΔTd_REF ... (16) Tdh_REF= MAX (Td_REF−ΔTd_REF, 0) (17) Expression (17) is expressed as Td_REF−ΔTd_REFWhat's with 0
The larger one is Tdh _REFRepresents that. Then
Proceeding to step S57, the clutch mechanism 17 is connected.
Control signal is output, and then the process proceeds to step S58.
And the actual front wheel steering angle, that is, the actual front steering angle from the steering angle sensor 21.
Change the wheel steering angle δ to the target front wheel steering angle δ^*Control to match
A signal is generated and output to the automatic steering motor 16.
Also, the correction value Tdh of the pressing pressure _REFControl that can cause
A signal is generated and output to the hydraulic unit 62. So
And return to the main program.

On the other hand, if the switch information from the automatic steering switch 24 is "OFF" in step S52, that is, if the automatic steering is not instructed, the flow shifts to step S59 where a control signal for releasing the clutch mechanism 17 is issued. Output, and then the process proceeds to step S60, wherein step S51 is performed.
And generates a control signal capable of generating the pressing pressure Td _REF calculated in step (1), and outputs the control signal to the hydraulic unit 62. Then, the process returns to the main program.

Therefore, when the automatic steering operation is not instructed, the process proceeds from step S1, S2, S3, and S51 to step S60 from step S52 through step S59, and the longitudinal acceleration X _G , the lateral acceleration Y _G and the left and right wheel are determined. and outputs a control signal capable of generating pressure Td _REF pressing of the differential limiting clutch 63 calculated based on the left and right wheel speeds differentially based on the speed detection value to the hydraulic unit 62. This allows the hydraulic unit 62 to operate the differential limiting clutch 6 according to the control signal.
3 and is controlled in the same manner as in the normal differential limiting control.

When the automatic steering switch 24 is controlled to the ON state, when the vehicle is traveling straight, the process proceeds from step S52 to step S55 via step S53, and the correction amount ΔTe _REF is set to ΔTe _REF = 0. In step S56, the pressing pressure Td _REF is corrected.
Since Te _REF is ΔTe _REF = 0, no correction is performed, and the same control as in the normal differential limiting control is performed, and the automatic steering control is performed.

Then, as shown in FIG. 4 (a), when the lateral deviation y increases in the automatic steering control process while the vehicle is traveling straight, the target front wheel steering angle δ ^* is corrected in order to correct this. However, when the vehicle speeds | V | and | Y _G | do not exceed the thresholds | V _TH | and | Y _GTH |, that is, when the vehicle is not turning sharply, the process proceeds from step S53 to step S55. Then, the control at the time of the normal differential limiting control is performed.

Then, from this state, as shown in FIG. 4B, when the vehicle shifts to the turning state while accelerating, the target front wheel steering angle δ ^* increases accordingly, and as shown in the state A, the vehicle moves straight ahead. To the turning state. And the vehicle speed |
V | and lateral acceleration | Y _G | are thresholds | V _TH | and | Y
_GTH |, the process proceeds from step S53 to step S54, and the correction amount ΔTe _REF is set according to the target front wheel steering angle δ ^*.
There is calculated, pressure correction value Tdh _REF pressed on the basis of the equation because accelerating (16) is calculated (step S56).

At this time, the correction amount ΔTe _REF is set to a larger value as the target front wheel steering angle δ ^* increases.
During acceleration, the pressing pressure correction value Tdh _REF is corrected to a larger value as the target front wheel steering angle δ ^* increases. Therefore, at the time of turning acceleration, the differential limiting amount calculated in the differential limiting control, that is, the pressing pressure of the differential limiting clutch 63 is corrected in a direction in which Tdh _REF is further increased in accordance with the target front wheel steering angle δ ^* , That is, since the correction is made in the oversteer direction, the turning performance of the vehicle is improved.

Then, as shown in state B from the accelerated turning state, when the vehicle is turned closer to the inside of the turn, the lateral deviation is corrected to the outside of the turn, so that the target front wheel steering angle δ ^* decreases and the correction amount ΔTe _{REF accordingly.} Decreases, and the pressing pressure correction value T
dh _{REF is} also reduced, the straight running stability of the vehicle is improved, and correction to the outside of the turning of the vehicle is performed with smooth vehicle behavior.

[0115] Then, when the transition from the turning state to the braking state, the vehicle speed | V | and the lateral acceleration | Y _G | threshold | V _TH
When | Y _GTH | is exceeded, the flow shifts from step S53 to step S54 to calculate a correction amount ΔTe _REF according to the target front wheel steering angle δ ^*, and corrects the pressing pressure Td _{REF in} step S56. that, this time, because it is braking, the equation (17) corrected based on is performed, the pressing is performed correction in a direction to decrease the pressure Td _REF, this time the target front-wheel steering angle [delta] ^* greater Correction amount ΔTe
_{Since REF} is increased and the pressing pressure correction value Teh _REF is corrected so as to decrease, during turning braking, the pressing pressure of the differential limiting clutch 63 decreases as the target front wheel steering angle δ ^* increases, that is, in the oversteer direction. , The turning performance of the vehicle is improved.

Then, as shown in state B from the braking turning state, when the vehicle moves toward the inside of the turn, the lateral deviation is corrected to the outside of the turn, so that the target front wheel steering angle δ ^* decreases and the correction amount ΔTe _{REF accordingly.} Decreases, the pressing pressure correction value Tdh _REF increases. Therefore, the correction in the oversteer direction is weakened as the target front wheel steering angle δ ^* decreases, so that the straight running stability of the vehicle is improved.

Therefore, in this case, the same operation and effect as those of the first embodiment can be obtained. Further, since the steering characteristic is changed only when it is determined that the vehicle is in a sharp turning state in the process of step S53, the lateral acceleration Y _G is large, that is, the left and right load moving amounts are large, and the differential limiting control is performed. Therefore, the steering characteristic can be changed only in a state where the effect of the change of the steering characteristic can be sufficiently obtained, and the steering characteristic can be changed efficiently.

Note that, in the fourth embodiment,
Target front wheel steering angle δ^*Correction amount ΔTe based on_REFCalculate
Was explained, but the target front wheel steering
Angle δ ^*Δδ^*To calculate based on
Also, the target front wheel steering angle δ ^*And the change amount Δδ^*Based on
May be calculated. Also, yaw rate sen
The actual front wheel steering angle δ_FTarget yaw rate from vehicle speed V
Gφ_REFAnd the target yaw rate φ_REFAnd yaw rate
From φ, it is determined whether the yaw rate of the vehicle is in the convergence direction.
And the correction amount ΔTe_REFTo calculate
May be.

Further, in each of the above embodiments, the vehicle having the power steering has been described. However, the present invention can be applied to a vehicle having no power steering. Further, of the above embodiments, only in the second embodiment, based on the vehicle sideslip angle βc,
Although the case where the stability of the vehicle behavior is determined has been described, it is needless to say that the present invention can be applied to the first, third, and fourth embodiments.

Further, of the above embodiments, the fourth embodiment
Only in the embodiment, the lateral acceleration Y _GAnd vehicle speed V
To judge whether the vehicle is in a sharp turn
In the first to third embodiments, a description has been given of the case.
However, it goes without saying that it can be applied.

[Brief description of the drawings]

FIG. 1 is a system configuration diagram showing a first embodiment of the present invention.

FIG. 2 is a flowchart illustrating an example of a processing procedure of automatic steering and attitude change suppression control processing.

3 is a characteristic diagram of a control gain KS _1.

FIG. 4 is an explanatory diagram for explaining the operation of the present invention;

FIG. 5 is a system configuration diagram showing a second embodiment of the present invention.

FIG. 6 is a flowchart illustrating an example of a processing procedure of automatic steering and driving force distribution control processing.

7 is a characteristic diagram of a control gain KS _2.

FIG. 8 is a system configuration diagram showing a third embodiment of the present invention.

FIG. 9 is a flowchart illustrating an example of a processing procedure of automatic steering and rear wheel steering control processing.

10 is a characteristic diagram of a control gain KS _3.

11 is a characteristic diagram of a control gain Ky ₁ and Ky _2.

FIG. 12 is a system configuration diagram showing a fourth embodiment of the present invention.

FIG. 13 is a flowchart illustrating an example of a processing procedure of automatic steering and differential limit control processing.

14 is a characteristic diagram of a control gain KS _4.

[Explanation of symbols]

 Reference Signs List 1FL, 1FR Front wheel 1RL, 1RR Rear wheel 10 Control unit 16 Automatic steering motor 17 Clutch mechanism 21 Steering angle sensor 22FL-21RR Wheel speed sensor 24 Automatic steering switch 25 Monocular camera 26 Camera controller 30 Steering mechanism 34 Hydraulic cylinder 36 Vertical acceleration sensor 37 Longitudinal acceleration sensor 38 lateral acceleration sensor 39 accelerator opening sensor 40 brake switch 41 engine 42 yaw rate sensor 43 transfer 43a clutch mechanism 50 hydraulic unit 53 actuator unit 54 electric motor 55 rear wheel steering mechanism 56a, 56b rear wheel steering angle sensor 61 differential Limiting device 62 Hydraulic unit 63 Differential limit clutch

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B62D 113: 00 B62D 113: 00 137: 00 137: 00 (72) Inventor Taku Takahama Kanagawa-ku, Yokohama-shi, Kanagawa 2 Takaracho Nissan Motor Co., Ltd. (72) Inventor Hiromitsu Toyoda 2 Takaracho, Kanagawa-ku, Yokohama-shi, Kanagawa Prefecture Nissan Motor Co., Ltd. F-term (reference) 3D032 CC48 DA03 DA24 DA86 DC38 DD17 EA05 EA06 EB16 EB17 EC34 3D033 CA02 CA04 CA13 CA14 CA17 CA21 CA29 5H180 AA01 CC04 LL01 LL02 LL09

Claims (10)

[Claims] 1. A target steering angle of a steered wheel for maintaining a lane is calculated, and a steering actuator is controlled so that the target steering angle and the actual steering angle of the steered wheel coincide with each other to selectively control the steered wheel. Automatic steering means, and a steering characteristic changing means capable of changing a steering characteristic of a vehicle, wherein the steering characteristic changing means controls the steered wheels by the automatic steering means. When the steering amount is large or when the steering amount is controlled in the increasing direction, the steering characteristic is changed in a direction to improve the turning performance of the vehicle, and when the steering amount is small or the steering amount is decreased. The lane keeping device is adapted to change the steering characteristic in a direction to improve the running stability of the vehicle when the vehicle is running. 2. The automatic steering device controls the steered wheels according to a yaw angle of the vehicle with respect to a traveling lane, a lateral deviation of the vehicle within the traveling lane, and a curvature ahead of the traveling lane. The lane keeping device according to claim 1, wherein 3. The steering characteristic changing means includes a roll stiffness distribution control device capable of changing a roll stiffness distribution before and after the vehicle, a driving force distribution control device capable of changing a front and rear drive force distribution in a four-wheel drive vehicle, and a front wheel. And a four-wheel steering control device capable of steering control of a rear wheel, or a differential limit control device capable of changing a differential limit amount of a drive wheel.
Or the lane keeping device according to 2. 4. The roll stiffness distribution control device changes a steering characteristic by changing a damping force for attenuating a vehicle body vibration at a front wheel position and a rear wheel position. The damping force at the front wheel position is made larger than the damping force at the front wheel position when the damping force is made larger than the damping force at the front wheel position and the running stability of the vehicle is improved. 3. The lane keeping device according to 3. 5. The driving force distribution control device changes a steering characteristic by changing a distribution ratio of a driving force transmitted from a driving source to a front wheel and a rear wheel, and improves a turning characteristic of the vehicle when the turning characteristic is improved. 4. The lane keeping device according to claim 3, wherein the distribution of the driving force to the front wheels is increased when the distribution of the driving force to the wheels is increased to improve the running stability of the vehicle. 6. The four-wheel steering control device changes a steering characteristic by changing a steering amount of a non-steered wheel,
The feature is that when the turning performance of the vehicle is improved, the steering amount of the non-steered wheels to the same phase is reduced, and when the running stability of the vehicle is improved, the steering amount of the non-steered wheels to the same phase is increased. The lane keeping device according to claim 3, wherein 7. The differential limit control device changes a steering characteristic by changing a differential limit amount of a drive wheel, and at the time of turning acceleration, sets the differential limit amount to improve the turning performance of the vehicle. When increasing and improving the running stability of the vehicle, the differential limiting amount is reduced, and during turning braking,
4. The vehicle according to claim 3, wherein the differential limiting amount is reduced when the turning performance of the vehicle is improved, and the differential limiting amount is increased when the running stability of the vehicle is improved. Lane keeping device. 8. A turning degree detecting means for detecting a turning degree of the vehicle, wherein the steering characteristic changing means is constituted by a plurality of control devices of the control devices, and the turning degree detected by the turning degree detecting means is provided. The lane keeping device according to claim 3, wherein a control device to be operated is switched in accordance with the vehicle speed. 9. A turning state detecting means for detecting a turning state of the vehicle, wherein the steering characteristic changing means changes the steering characteristic when the turning state detecting means detects a sharp turning state. The lane keeping device according to any one of claims 1 to 8, characterized in that: 10. A vehicle behavior detecting means for detecting a vehicle behavior, wherein the steering characteristic changing means is configured to execute the steering characteristic changing when the running stability of the vehicle is predicted to be impaired based on the detection result by the vehicle behavior detecting means. The lane keeping device according to any one of claims 1 to 9, wherein the steering characteristic is not changed in a direction to improve the turning performance of the vehicle.